The new approach to Juhl's operators which I present in this article follows a method that I used for similar problems, in the context of the restriction problem for a pair \((G\times G,G^{\prime })\)  where \(G^{\prime }=G\)  embedded diagonally in \(G\times G\) . I was influenced by a reminiscence of the \(\Omega \) -process which yields both the transvectants and the Rankin–Cohen brackets. These operators may be viewed as covariant bi-differential operators for the group \({\rm SL}(2,\mathbb {R})\) , or symmetry breaking differential operators from \({\rm SL}(2,\mathbb {R}) \times {\rm SL}(2,\mathbb {R})\)  to its diagonal subgroup. For a presentation of these classical results see Section 5 of [1]} for a quick overview or [2]} for a thorough exposition of the transvectants.
